On The Benefits Of Filling 3D Prints With Spray Foam

November 29, 2025 by Maya Posch No comments

Closed-cell self-expanding foam (spray foam) is an amazing material that sees common use in construction. But one application that we hadn’t heard of before was using it to fill the internal voids of 3D printed objects. As argued by [Alex] in a half-baked-research YouTube video, this foam could be very helpful with making sure that printed boats keep floating and water stays out of sensitive electronic bits.

It’s pretty common knowledge by now that 3D printed objects from FDM printers aren’t really watertight. Due to the way that these printers work, there’s plenty of opportunity for small gaps and voids between layers to permit moisture to seep through. This is where the use of this self-expanding foam comes into play, as it’s guaranteed to be watertight. In addition, [Alex] also tests how this affects the strength of the print and using its insulating properties.

The test prints are designed with the requisite port through which the spray foam is injected as well as pressure relief holes. After a 24 hour curing period the excess foam is trimmed. Early testing showed that in order for the foam to cure well inside the part, it needed to be first flushed with water to provide the moisture necessary for the chemical reaction. It’s also essential to have sufficient pressure relief holes, especially for the larger parts, as the expanding foam can cause structural failure.

As for the results, in terms of waterproofing there was some water absorption, likely in the PETG part. But after 28 hours of submerging none of the sample cubes filled up with water. The samples did not get any stronger tensile-wise, but the compression test showed a 25 – 70% increase in resistance to buckling, which is quite significant.

Finally, after tossing some ice cubes into a plain FDM printed box and one filled with foam, it took less than six hours for the ice to melt, compared to the spray foam insulated box which took just under eight hours.

This seems to suggest that adding some of this self-expanding foam to your 3D printed part makes a lot of sense if you want to keep water out, add more compressive strength, or would like to add thermal insulation beyond what FDM infill patterns can provide.

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A Flexible Light Inspired By IKEA

November 29, 2025 by Jenny List 4 Comments

The IKEA SMÅSNÖRE is a flexible silicone rod with an embedded LED strip, attached at each end to a base. It’s eye-catching enough, and it has the useful property of providing a diffuse light from multiple angles that makes it a promising candidate for a work lamp. That’s enough for [Daniel James] to create his own lamp on a similar vein.

The electronics of his lamp are straightforward enough: a 12 volt LED strip whose brightness is controlled by a Pi Pico in response to a potentiometer as a brightness control. It’s not quite stiff enough to form the arch itself, so he’s created a 3D printed chain that forms the structure of the lamp. Similar to a bicycle chain in the way it’s constructed, it has individual links that slot together and pivot. The electronics are in the printed base at one end.

We like this lamp a lot, for the light it gives on the bench and for the ingenuity of the printed chain. We might even make one for ourselves.

Building A Simple Ribbon Synth

November 29, 2025 by Lewin Day No comments

The usual input device for playing a synthesizer is the good old piano keyboard. However, you don’t have to stick to such pedestrian interfaces when making music. [Daisy] has a fun build that shows us how to put together a ribbon synth that makes wonderful little noises.

Naturally, the heart of the build is a ribbon potentiometer (also known as soft pots). It’s essentially a touch sensitive strip that changes in resistance depending on where you touch it. You can slide your finger up and down to vary the output continuously; in musical contexts, they can behave rather like a fretless instrument. [Daisy] employs one of these potentiometers in such a role by hooking it up to a Daisy Seed microcontroller board, which reads it with an analog-to-digital converter (ADC). The resistance values are used to vary the pitch of a dual-saw synthesizer programmed in the plugdata framework.

We’ve featured some other great ribbon synths over the years, too, like this tribute to the Eowave Persephone. They’re not the ideal choice for those that prefer their notes on pitch, but they’re beautifully fun to play with when you’re getting a little more experimental.

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How To Print PETG As Transparently As Possible

November 29, 2025 by Lewin Day 4 Comments

PETG filament can be had in a variety of colors, just like any other. You can even get translucent or transparent forms if you want to print something vaguely see-through. But if you’re looking for a bit more visually impressive, you might like to pick up a few tips from [Tej Grewal] on making sure your prints come out as clear as possible.

Standard print settings aren’t great for transparency.

It all comes down to pathing of the 3D printer’s hot end. If it’s zigzagging back and forth, laying down hot plastic in all different orientations from layer to layer, you’re going to get a hazy, ugly, result that probably doesn’t look very see-through at all.

However, you can work around this by choosing slicer settings that make the tool pathing more suitable for producing a clearer part. [Tej] recommends going slow — as little as 20 mm/s during printing. He also states that removing top and bottom shells and setting wall loops to 1 can help to produce a part that’s entirely infill. Then, you’ll want to set infill to 100% and the direction to 0 or 90 degrees. This will ensure your hot end is just making long, straight strokes for layer after layer that will best allow light to pass through. You’ll also want to maximize nozzle flow to avoid any unsightly gaps or bubbles in your print.

[Tej] demonstrates the technique by creating a cover for a display. By using the settings in question, he creates a far more transparent plate, compared to the original part that has an ugly zig-zagging haze effect. You’re not going to get something optically clear this way; the final results are more lightly frosted, but still good.

Transparency will never be something 3D printers are great at. However, we have seen some interesting post-processing techniques that will blow your mind in this regard.

Portable Plasma Cutter Removes Rust, Packs A (Reasonable) Punch

November 29, 2025 by Donald Papp 7 Comments

[Metal Massacre Fab Shop] has a review of a portable plasma cutter that ends up being a very good demonstration of exactly what these tools are capable of. If you’re unfamiliar with this kind of work, you might find the short video (about ten minutes, embedded below) to be just the right level of educational.

Plasma cutters work by forcing compressed air through a small nozzle, and ionizing it with a high voltage. This process converts the gas into a very maneuverable stream of electrically-conductive, high-temperature plasma which can do useful work, like cutting through metal. The particular unit demonstrated also has a rust removal function. By operating at a much lower level, the same plasma stream can be used to give an effect not unlike sandblasting.

Of course, an economical way to cut metal is to just wield a grinder. But grinders are slow and not very maneuverable. That’s where a plasma cutter shines, as [Metal Massacre Fab Shop] demonstrates by cutting troublesome locations and shapes. He seems a lot more satisfied with this unit than he was with the cheapest possible (and misspelled!) plasma cutter he tried last year.

And should you want a plasma cutter, and aren’t afraid to salvage components? Consider building your own.

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Instant Sketch Camera Is Like A Polaroid That Draws

November 28, 2025 by Lewin Day 11 Comments

These days, everyone’s got a million different devices that can take a passable photo. That’s not special anymore. A camera that draws what it sees, though? That’s kind of fun. That’s precisely what [Jens] has built—an instant sketch camera!

The sketch camera looks like a miniature drawing easel, holding a rectangular slip of paper not dissimilar in size to the Polaroid film of old. The 3D-printed frame rocks a Raspberry Pi controlling a simple pen plotter, using SG90 servos to position the drawing implement and trace out a drawing. So far, so simple. The real magic is in the image processing, which takes any old photo with the Pi camera and turns it into a sketch in the first place. This is achieved with the OpenCV image processing library, using an edge detection algorithm along with some additional filtering to do the job.

If you’ve ever wanted to take Polaroids that looked like sketches when you’re out on the go, this is a great way to do it. We’ve featured some other great plotter builds before, too, just few that are as compact and portable as this one. Video after the break.

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